The Lighthouse Winmore, chartered by Taiwanese company Billions Bunker Group, was seized by South Korea authorities.

South Korea has seized a ship suspected of illegally supplying oil to North Korea, the center of a brewing international controversy on the peninsula that has widened to China and President Trump.

Authorities in Seoul revealed Friday that they had briefly taken the Lighthouse Winmore, a tanker registered in Hong Kong that allegedly transferred fuel to a vessel from the isolated hermit kingdom.

The Lighthouse Winmore, which the U.S. recently called to be on a United Nations blacklist of ships involved with North Korea, was seized and inspected at the Yeosu port in late November, according to news agency Yonhap.

It allegedly transferred 600 tons of oil, part of what the newspaper Chosun Ilbo reported was a trend of Chinese ships transferring oil 30 times since October.

News of the alleged transfers on Thursday led Trump to say that China had been “caught RED HANDED” getting around sanctions on North Korea meant to help curb their nuclear program.

He said in a tweet that he was “very disappointed” in Beijing and added in an interview published Thursday evening that he was reconsidering his "soft" trade stance with the people's republic.

The U.S. Treasury released photos of an alleged transfer in November alongside a list of sanctions that includes Chinese companies.

North Korean leader Kim Jong Un's nuclear program has led to UN sanctions including ones on oil.

(KCNA/REUTERS)

China has denied any involvement and Foreign Ministry spokeswoman Hua Chunying said "we will never allow Chinese citizens and enterprises to engage in activities that violate Security Council resolutions."

The information released by South Korea authorities on Friday did not include details about possible involvement by the Chinese government.

Despite being flagged as Hong Kong, the Lighthouse Winmore has actually been chartered by a Taiwanese company called Billion Bunker Group.

China is North Korea's trading partner, and has repeatedly come under scrutiny as the international community hopes to force Pyongyang away from the nuclear program that is now bolstered by missiles able of delivering a warhead to the U.S. East Coast.

Secretary of State Rex Tillerson said in a commentary Thursday that Beijing "could and should do more" to implement the United Nations restrictions.

Current UN sanctions create a limit for the amount of oil countries are allowed to send to North Korea each year, but ban ship-to-ship transfers.